Transcript decomp

Taphonomy
Defined by Efremov (1940) as “the
study of the accumulation and
modification of osteological
assemblages from a site formation
perspective.”
Goals of Taphonomy
• Reconstruct paleoenvironments
• Determine which factors cause the
differential destruction or attrition of bone
• Understand selective transport of remains
• Discriminate human from nonhuman agents
of bone modification
Forensic Anthropology and Taphonomy
• Forensic Anthropology shares the last three
of these goals, but are also interested in:
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decomposition rates and patterns
disarticulation
dispersion of body parts
modification of soft tissue and bone
• In order to show
– time and circumstances of death
– postmortem vs. antemortem/perimortem
conditions
– identifying factors
Forensic Taphonomy
• Can therefore be described as the use of
taphonomic models to
– reconstruct postmortem interval
– reconstruct conditions before and after
deposition
– discriminate the products of human behavior
from those created by the earth’s biological,
physical, chemical and geological subsystems
• Autochthonous
– where death occurred
• Allochtonous
– different from where death occurred
A Forensic Taphonomic Model
• Four dimensions
– objects
• human remains
– space
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on the surface
within other environments (e.g. water)
buried
allocthonous vs. autochthonous
– modification of objects
– cultural dimension
• cause and manner
• investigator bias
• Two major temporal concerns
– perimortem interval
• includes the timing of specific events such as trauma
as they relate to the time of death
– postmortem interval
• ordinal (sequence of events)
• interval (absolute time)
• ratio (relative to some other temporal sequence)
Perimortem Interval
• Estimating time of injury is difficult in the
best cases
• Must be able to determine conditions under
which certain taphonomic conditions come
into play
– but these processes are not precise, so the
boundry between life and death becomes
blurred
Postmortem Interval
• Also imprecise
• After death, the muscles of the body
become flaccid
• Within 1-3 hours the muscles become
increasingly rigid and the joints freeze
– rigor mortis
• All muscles begin to stiffen simultaneously,
but it is noticeable in smaller muscle groups
first
Rigor mortis
• Complete rigor takes 10-12 hours to
develop under ideal conditions
– 70-75 degrees Fahrenheit
• The body remains stiff 24-36 hours
• Heavily impacted by temperature and other
environmental conditions, body size, activity
prior to death, etc.
Livor Mortis
• Also known as lividity
• discoloration of the body after death due to
gravitational settling of blood
• Usually noticeable approximately 1 hour
postmortem, apparent early often
• Becomes fixed in about 8-10 hours
• Visible until decomposition changes the
color of the body
Algor Mortis
• Normal cooling of a body which takes place
as the body equilibrates with the external
temperature
• Occurs at an approximate rate of 1.5
degree F an hour
– this is obviously dependant on external
temperature
Decomposition
• In general, occurs in stages
– after rigor passes, green discoloration of the skin
become evident
• generally begins on the abdomen about 24 hours after
death
– The body will begin to swell (bloat) due to
production of gas by bacteria in the large
intestine
• may begin within 96 hours after death, sooner if warm
or wet
– As the body bloats, the outer layers of the skin
begin to slip off the body, as will the hair and
nails
• Also during bloat body fluids may purge
through the nose and mouth and other
orifices.
• At about the same time, the blood within
vessels degenerates and darkens, giving
the skin a marbled appearance
Order of Decomposition
• Intestines, stomach, accessory digestive
organs, heart, blood, circulatory system
• air passages and lungs
• kidneys and bladder
• brain and nervous tissues
• skeletal muscles
• connective tissues